routing ground wire from indoor sub-panel

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Old 05-18-10, 12:45 PM
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routing ground wire from indoor sub-panel

I'm running a feeder to a detached shop/office, via 3 underground conductors in conduit. They pass through two walls ( in 1 each 90 degree sweep around a corner ) to the sub-panel.

I need to ground the circuit(s), but I'm hesitant to pass a bare ground wire through the walls.

Am I to insulated it? Run it in metallic or non-metallic conduit? Or am I just worrying too much over nothing?
 
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Old 05-18-10, 01:07 PM
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The ground wire must run through the same conduit as the hot and neutral conductors. The conduit must be continuous box to box.

Metallic or non-metallic depends on the type of building, potential damage, burial depth, type of circuit, etc.
 
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Old 05-18-10, 01:18 PM
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Ok ...

but NEC 2008 has a section for separate grounding systems for detached buildings: 250.32 .

What is not clear is what sort of protection the grounded conductor should or must have. If it were an outside panel I'd just run it bare to the first rod.

I found where you had posted this :http://forum.doityourself.com/electr...ml#post1563327
earlier. Does this address my question?
 
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Old 05-18-10, 01:31 PM
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Okay that makes some more sense. You're talking about the grounding electrode conductor; the "grounding conductor" and "grounded conductor" are different.

If the GEC is #8, it should run through wall spaces, bored holes and stapled similar to romex installation. It should be sleeved in PVC conduit where exposed outdoors for protection. Don't use metal conduit in this case.

If the GEC is #6 or larger it can run unprotected through the wall cavity and outdoors to the ground rod simply stapled to the building exterior or similarly fastened.
 
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Old 05-18-10, 01:52 PM
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Thank you!

Grounding Electrode Conductor - exactly so.
 
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Old 05-18-10, 02:20 PM
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I'm running a feeder to a detached shop/office, via 3 underground conductors in condui
If the conduit is PVC you must also have a ground wire.
 
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Old 05-18-10, 03:39 PM
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A grounding conductor in the conduit?

This puts me up to 4 conductors. Does this mean I have to derate the conductors to 80%?

I was running 3 each #2 copper for a 100A service in 2" schedule 80 PVC.
 
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Old 05-18-10, 03:49 PM
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Originally Posted by Ecclesiastes View Post
This puts me up to 4 conductors. Does this mean I have to derate the conductors to 80%?
Nope, you have to derate after 9 current carrying conductors. In your case, you only have two (the two hots). In theory, the neutral is not current carrying since a perfectly balanced load will provide 0A on the neutral conductor. Though this will never happen in real life, you still don't have to consider it a current carrying conductor.
 
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Old 05-18-10, 05:18 PM
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Originally Posted by Zorfdt View Post
Nope, you have to derate after 9 current carrying conductors. In your case, you only have two (the two hots). In theory, the neutral is not current carrying since a perfectly balanced load will provide 0A on the neutral conductor. Though this will never happen in real life, you still don't have to consider it a current carrying conductor.
Not sure where you get your information. Neutrals are always counted as current carrying conductors for derating purposes. When talking about having 9 CCC's in a pipe, neutrals are always counted.
 
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